This invention relates to surgical staplers and more particularly, it concerns an improved multi-staple cartridge for such staplers by which uniform tissue compression and staple driving forces are assured for individual staples irrespective of variations in tissue thickness in the area of multiple staple application.
U.S. Pat. Nos. 3,080,564-Strekopitov et al and 3,275,211-Hirsch et al exemplify basic structural and functional characteristics of surgical staplers currently in use. In staplers of the general type disclosed in these patents, a multi-staple cartridge is adapted to be retained along the face of a head jaw parallel to and movable in relation to an anvil carried along the face of another jaw of the stapler. In use, tissue to be stapled is received between the jaws which are then adjusted to compress the tissue between the leading face of the staple cartridge and the anvil. Thereafter, the stapler is actuated to drive all staples in the cartridge simultaneously through the tissue and against the anvil for deflecting or bending the projecting legs of each staple inwardly and back into the tissue so that each staple so placed assumes a configuration resembling a "B".
The distance between the face of the cartridge and the anvil after tissue compressing adjustment of the stapler jaws falls within a range dictated by staple size. In particular, each staple size has a safe working range which represents the difference between the maximum and minimum separation of the anvil and cartridge face which will insure proper bending of the staple legs to secure the stapled tissues. The maximum safe distance of separation is determined by the least amount of staple leg bending needed for staple retention of the tissues whereas the minimum safe distance of separation is determined by the ability of the staple to retain the tissues in adequate proximity for healing. The specific distance of jaw face separation within the safe working range of a particular staple size is largely a matter of judgment by the surgeon though devices are available for measuring the combined thickness of tissues to be stapled.
While the present state of surgical stapler development accommodates a range of tissue thickness for a specific staple size, there remains no provision for variation in the thickness of tissues over the length of a line (or double line) of staples inserted simultaneously from a single cartridge. In certain organs, such as the large intestine, tissue thickness may vary considerably over the length of a multi-staple cartridge face. Although the thickest tissue may fall within the safe working range of the size of staples in a given cartridge, the legs of all such staples will be bent to the same configuration because of the common distance of separation between the stapler jaws at the time of final staple application. As a result, staples applied in relatively thin sectors of tissue will be too loose to completely seal the tissue, can lead to bleeding, leakage and other complications. There is a need therefore for increased accommodation of tissue thickness variation in multi-staple surgical staplers.